1. Field of the Invention
The present invention relates to a variable-profile optical device and optical element in which a curvature can continuously be changed, particularly to a small-sized variable-profile optical device and optical element to which a semiconductor technique is applied.
Moreover, the present invention relates to a variable-profile mirror and variable-profile optical element, particularly to a small-sized variable-profile mirror and variable-profile optical element to which a semiconductor technique is applied in a variable-profile optical device having a curvature able to be continuously varied.
2. Description of the Related Art
In micro optics such as an optical pickup, for the purpose of simplifying a mechanism related with focusing in which an electromagnetic actuator is used, there has heretofore been proposed a micro variable focus mirror in which the curvature of a reflective surface can be changed.
Moreover, also in small-sized optics for camera, application of the variable focus mirror can largely contribute to miniaturization.
In a variable focus mirror when a so-called micro electromechanical system (MEMS) technique with a semiconductor manufacturing technique applied thereto is used, low-cost high-precision production can be expected.
Known driving methods for this type of variable-profile mirror include using an electrostatic attractive force, as described in Jpn. Pat. Appln. KOKAI Publication No. 2-101402, a piezoelectric effect, as described in Jpn. Pat. Appln. KOKOKU Publication No. 3-81132, fluid pressure, as described in Jpn. Pat. Appln. KOKAI Publication No. 1-219801, and the like.
These methods have advantages and disadvantages, but the method of using fluid pressure is suitable for use in which a relatively large displacement to a convex surface from a concave surface is required.
As an example of a variable-profile mirror driven by fluid pressure, the method described in Jpn. Pat. Appln. KOKAI Publication No. 1-219801 will briefly be described with reference to FIG. 26.
A variable focus mirror 1 is constituted of a shell 2, chamber pressure adjustment apparatus 3, and reflective mirror 4.
A pressure chamber 5 is formed in the shell 2, and a holder 7 for holding the reflective mirror 4 in an airtight manner by O rings 6 is formed in an opening of the shell.
The pressure chamber 5 is connected to a pressure gauge 8 and piping 9 of the chamber pressure adjustment apparatus 3.
The piping 9 is branched into a compressor piping 9a and vacuum pump piping 9b, and the piping can appropriately be switched to a compressor 11a or a vacuum pump 11b by electromagnetic operation valves 10a, 10b. 
In the constitution, the switching is performed, when a controller 12 opens/closes the electromagnetic operation valves 10a, 10b. 
The reflective mirror 4 is formed of a thin plate, and a reflective surface 13 is coated with a reflective material such as aluminum.
In the variable focus mirror 1 constituted as described above, to obtain a concave reflective surface 13a, the electromagnetic operation valve 10a is closed, and the electromagnetic operation valve 10b is opened by the controller 12.
In this case, when the pressure chamber 5 is connected to the vacuum pump piping 9b, a negative pressure is produced by the vacuum pump 11b. 
Therefore, in this case, the reflective mirror 4 is deflected toward the pressure chamber 5, and the concave reflective surface 13a is formed.
On the other hand, to form a convex reflective surface 13b of the reflective mirror 4, the. electromagnetic operation valve 10a is opened, and the electromagnetic operation valve 10b is closed by the controller 12.
In this case, when the pressure chamber 5 is connected to the compressor piping 9a, a positive pressure is produced by the compressor 11a. 
Therefore, in this case, the reflective mirror 4 is deflected away from the pressure chamber, and the convex reflective surface 13b is formed.
Furthermore, when the pressure of the pressure chamber 5 is controlled to be the same as an external pressure, the reflective surface 13 has a flat reflective surface 13c due to the elasticity thereof.
For the shape of the reflective surface 13, when the controller 12 is controlled based on a measured value of the pressure gauge 8, the reflective mirror 4 can continuously be set at an optional focal distance.
As compared with the electrostatic attractive force driving method in which the displacement amount is limited by the distance between electrodes, or the piezoelectric driving method in which it is difficult to obtain a large deflection because of limitation of the materials of the reflective surface, the variable-profile mirror whose driving source is fluid pressure is preferable particularly for use in which a broad range of focal distances are required.
The variable focus mirror of the above-described fluid pressure system has a problem that a pump or compressor is necessary and therefore it is very difficult to miniaturize the mirror.
Moreover, the above-described variable focus mirror of the fluid pressure system has complicated mechanisms such as a valve, and has a problem that efficiency or response is deteriorated due to the pump and pressure chamber channel.
Furthermore, since a uniform force is exerted on a deformable portion of the variable focus mirror in principle in the method of using fluid pressure, the deformed shape has rotational symmetry. However, since light is generally incident from an oblique direction in relation to a light path in the reflective optics, a large aberration is generated.
In this respect, the transmission type variable-profile optical device (i.e., a variable-profile lens) is advantageous. For example, in the conventional variable focus lens described in Jpn. Pat. Appln. KOKOKU Publication No. 3-27090 (corresponding to Jpn. Pat. KOKAI Publication No. 60-114802), as the deformable member needs to be sealed in a container, there is a problem that assembly is complicated, and the lens is not suitable for miniaturization.
Moreover, for the above-described variable focus mirror of the fluid pressure system, because the mechanism is complicated, it is difficult to miniaturize the mirror, and there is a problem that the efficiency and response are deteriorated.
Furthermore, the above-described variable focus mirror of the fluid pressure system is applied particularly to the optics in which the light is obliquely incident. In this case, the aberration is generated in principle, and this may cause serious problems, depending on the use.